Freshwater aquaculture

Unit 4 - Cultivable fish and their culture methods

4.3.1. Systems of management for reducing HIG
There are three to four systems of grow-out culture of freshwater prawns, the are:

1) Continuous System:
This system involves regular stocking of post larvae (PL) and selective harvesting of prawns of marketable size. There is no defined “cycle” of operation and ponds are drained only occasionally. This system can be practiced in places where there is year – round water availability and optimum temperature is present throughout the year. Also if selective harvesting is inefficient, large dominant prawns remain and have negative impact on the PLs which are introduced at subsequent stocking, resulting in lower average growth rate.
Long terms continuous system is not recommend for above reasons.

2) The Batch System:
Batch system consists of stocking the pond once and allowing the individuals to grow to average market size. The ponds are drained totally and harvested HIG remains as a problem in this system.

3) The combined system:
The ponds are stocked only once. Cull – harvesting starts when the first prawns reach marketable size, removing the fast growing prawns for sale and leaving the smaller ones to grow with less impact of HIG. After several cull- harvesting, the ponds are finally drain-harvested. The total cycle usually lasts for about 9-12 months in tropical regions. This is a recommended system for culture of freshwater prawns for better management of HIG to more uniformed sized prawns.